Plate-Type Heat Pump Air Conditioner Heat Exchanger for a Unitary Heat Pump Air Conditioner

ABSTRACT

A plate-type heat exchanger having a first heat exchanger portion configured to receive a refrigerant flow and a hot side coolant flow having a lower temperature than the refrigerant flow, a second heat exchanger portion configured to receive the refrigerant flow exiting from the first heat exchanger portion and a cold side coolant flow having a higher temperature than the refrigerant flow exiting from the first heat exchanger portion, and an internal heat exchanger portion sandwiched between the first heat exchanger portion and the second heat exchanger portion. The refrigerant flow through the plate type heat exchanger is in non-contact thermal communication with the hot side coolant flow and the cold side coolant flow. The cold side coolant flow transfers heat energy to the refrigerant, which in turn transfer that heat energy to the hot side coolant flow.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/396,211, PLATE-TYPE HEAT PUMP AIR CONDITIONER HEAT EXCHANGERFOR A UNITARY HEAT PUMP AIR CONDITIONER, filed on Feb. 14, 2012, whichclaims the benefit of U.S. Provisional Patent Application No.61/443,774, UNITARY HVAC SYSTEM, filed on Feb. 17, 2011.

TECHNICAL FIELD OF INVENTION

The present invention relates to a heating and air-conditioning systemfor an automotive vehicle; particularly, to a heat pump air-conditioningsystem; and more particularly, to a heat exchanger for a heat pumpair-conditioning system.

BACKGROUND OF INVENTION

For the comfort of the occupants in the passenger compartment, motorvehicles typically include dedicated air-conditioning systems andheating systems. The heating system includes a heater core locatedinside a heating, ventilating, and air conditioning (HVAC) module of thevehicle. The heater core is typically a liquid-to-air heat exchangerthat supplies thermal energy to the passenger compartment for comfortheating. A heat transfer liquid, such as a glycol based coolant, conveyswaste heat from an internal combustion engine to the heater core wherethe thermal energy from the heat transfer liquid is transferred to theambient air flowing through the heater core to the passengercompartment. With the advent of greater efficiency internal combustionengines, hybrid vehicles having smaller internal combustion engines, andespecially electrically driven vehicles, the amount of thermal energyavailable to provide comfort to occupants in the passenger compartmentmay not be adequate.

To provide supplemental heat to the passenger compartment for vehicleshaving smaller internal combustion engines, it is known to operate theair-conditioning system in heat pump mode. A typical motor vehicleair-conditioning system includes an evaporator located in the HVACmodule and a condenser located in the front engine compartment exposedto outside ambient air. A compressor circulates a two-phase refrigerantthrough the evaporator where it changes into a low pressure vapor phaseby absorbing heat from the passenger compartment. After the low pressurevapor is compressed to a high pressure vapor by the compressor, thevapor phase refrigerant is transferred to the condenser where the highpressure vapor is condensed into a high pressure liquid phase byreleasing the heat to the ambient air. The liquid phase is returned tothe evaporator through an expansion valve which converts high pressureliquid refrigerant to a low pressure mixture of liquid and vaporrefrigerant to continue the cycle. By operating the air-conditioningsystem in heat pump mode, the refrigerant flow is reversed, in whichcase the condenser absorbs heat from the outside ambient air byevaporating the liquid phase refrigerant and the evaporator releases theheat to the passenger compartment by condensing the vapor phaserefrigerant. One disadvantage to operating the air-conditioning systemin heat pump mode, since the low pressure side of the system when usedin air conditioning mode would become the high pressure side when usedin heat pump mode, is the increase in system complexity due to therequirement of having to reinforce the refrigerant plumbing throughoutthe system by using thicker gage tubing and fittings. There is also theneed to reinforce the evaporator to withstand the high pressurerefrigerant, and to install an additional expansion valve and receivertogether with additional associated plumbing. Another known disadvantageof operating the system in heat pump mode is that in cooler climates, asthe surface temperature of the condenser drop below 32° F., any moisturecondensed on the surface of the condenser is subject to freezing,therefore potentially reduces the system's efficiency or even damage thecondenser.

Electric heaters are known to be used to provide supplemental heat tothe passenger compartment for vehicles using the air-conditioning systemas a heat pump. In the coldest of climates, it is known that operatingthe air-conditioning system in heat pump mode is ineffective; therefore,additional electric heaters are required. However, for hybrid andelectrical vehicles, electrical heaters represent an increased currentdraw that significantly reduces the electric drive range.

Based on the foregoing, there is need for a heating system that providessupplementary heat to the passenger compartment of a motor vehicle thatdoes not require reversing the refrigerant cycle of the air-conditioningsystem or detrimentally impact the electric driving range.

SUMMARY OF THE INVENTION

The present invention relates to Unitary Heat Pump Air Conditioner(Unitary HPAC) for a Unitary HPAC System. The Unitary HPAC includes aplate-type HPAC heat exchanger having a plurality of plates withpredefined openings, a plurality of flow spaces adjacent the openings,and bosses about selected openings. The plates are arranged, stacked,and hermetically sealed between an upstream end plate and a downstreamend plate defining a first heat exchanger portion, a second heatexchanger portion, and an internal heat exchanger sandwichedtherebetween.

The first heat exchanger portion is configured to receive a refrigerantflow and a hot side coolant flow having a lower temperature than therefrigerant flow. The refrigerant flow is in non-contact thermalcommunication with the hot side coolant flow, whereby heat energy istransferred from the refrigerant flow to the hot side coolant flow.

The second heat exchanger portion is configured to receive therefrigerant flow exiting from the first heat exchanger portion and acold side coolant flow having a higher temperature than the refrigerantflow, wherein the cold side coolant flow is in non-contact thermalcommunication with the refrigerant flow, whereby heat energy istransferred from the cold side coolant flow to the refrigerant flow.

The internal heat exchanger portion is configured to receive therefrigerant flow exiting from the first portion heat exchanger beforebeing received by the second heat exchanger portion and the refrigerantflow from the second heat exchanger portion. The temperature of therefrigerant flow exiting the first heat exchanger portion is higher thantemperature of the refrigerant flow from the second heat exchangerportion. The refrigerant flow from the first heat exchanger portion isin non-contact thermal communication with the refrigerant flow from thesecond heat exchanger portion, whereby heat energy is transferred fromthe refrigerant flow exiting from the first heat exchanger portion tothe lower temperature refrigerant flow from the second heat exchangerportion before exiting the second heat exchanger.

The Unitary HPAC also includes an electrically driven compressor havinga high pressure discharge side hydraulically connected to the highpressure refrigerant inlet of first heat exchanger portion and a lowpressure intake side hydraulically connected to the low pressurerefrigerant outlet of second heat exchanger portion, and electricallydriven hot side coolant and cold side coolant pumps in hydrauliccommunication with the hot side coolant inlet and cool side coolantinlet, respectively.

The plate-type HPAC heat exchanger together with the associatedelectrically driven compressor and coolant pumps may be mounted onto aplatform or enclosing in a housing that is approximately the size of abread box, thereby providing a compact Unitary HPAC for a Unitary HPACSystem. Further features and advantages of the invention will appearmore clearly on a reading of the following detailed description of anembodiment of the invention, which is given by way of non-limitingexample only and with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

This invention will be further described with reference to theaccompanying drawings in which:

FIG. 1 a schematic flow diagram a Unitary Heat Pump Air ConditionerSystem (Unitary HPAC system) in accordance with the invention.

FIG. 2 shows an exemplary Unitary HPAC system operating in cooling mode.

FIG. 3 shows an exemplary Unitary HPAC system operating in heating mode.

FIG. 4 shows an embodiment of the Unitary HPAC in accordance with theinvention.

FIG. 5 shows another embodiment of the Unitary HPAC in accordance withthe invention having a Plate-type HPAC Heat Exchanger, electricallydriven compressor, and electrically driven coolant pumps.

FIG. 6 is a schematic cross-section of the Plate-type HPAC HeatExchanger of FIG. 5, showing the flow path of the hot and cold coolants,and flow path of refrigerant.

FIG. 7 shows and exploded view of the embodiment of the Plate-type HPACHeat Exchanger of FIG. 5.

DETAILED DESCRIPTION OF INVENTION

Referring to FIGS. 1 through FIG. 7 is a Unitary Heat Pump AirConditioner System (Unitary HPAC System) and two embodiments of aUnitary HPAC for use in a motor vehicle. The motor vehicle may be thatof one with an internal combustion engine, a hybrid vehicle having bothan internal combustion engine and an electric drive, or that of anelectric vehicle having an electric drive. The Unitary HPAC System is acompact hermetically sealed system that improves the overall efficiencyof the heating system and also provides cooling system to the motorvehicle, which improves the driving ranges of both hybrid and electricvehicles by, for example, minimizing the use an electric current, suchas that to power an electric heater. In essence, the Unitary HPAC systemprovides a dedicated refrigerant system in which the refrigerant cycledoes not need to be reversed in order for the Unitary HPAC system tooperate in heat pump mode. The Unitary HPAC system also provides aUnitary HPAC that is compact and easily installed in virtually anycompartment of a vehicle that is about the size of a bread box or asmall tool box. Further advantages of the Unitary HPAC System will bereadily appreciated by the reading of the disclosure below.

Shown in FIG. 1 is flow schematic of the Unitary HPAC System 10 having arefrigerant loop 12 in thermal communication with a cold coolant loop 14and a hot coolant loop 16. The main components of the refrigerant loop12 include a condenser 18, a refrigerant expansion device 20 such athermal expansion valve (TXV) 20, and an evaporator 22 hydraulicallyconnected in series. At the heart of the refrigerant loop is arefrigerant compressor 24 located downstream of the evaporator 22 andupstream of the condenser 18. The compressor 24 is responsible forcompressing and transferring a two-phase refrigerant, such as R-134a orR-1234yf, throughout the refrigerant loop 12 of the Unitary HPAC System10. The hot coolant loop 16 includes a hot side chiller 26 in thermalcommunication with the condenser 18 and a hot side coolant pump 28 thatcirculates a hot side coolant through the hot side chiller 26.Similarly, the cold coolant loop 14 includes a cold side chiller 30 inthermal communication with the evaporator 22 and a cold side coolantpump 32 that circulates a cold side coolant through the cold sidechiller 30. The hot side chiller 26 and cold side chiller 30 may be thatof a water jacket encasing the condenser 18 and evaporator 22,respectively, or may be part of a plate-type heat exchanger, which isdisclosed in greater detail below. The cold coolant loop 14 may absorbwaste heat energy from various heat sources throughout the vehicle, suchas the waste heat from the internal combustion engine or electronics,thereby cooling the various heat sources. The refrigerant loop 12transfers the heat energy from the cold coolant loop 14 to the hotcoolant loop 16, which in turns transfer the heat energy to various heatsinks throughout the vehicle, such as an occupant heat exchanger toprovide supplemental heat to the passenger compartment. The Unitary HPACSystem 10 effectively captures waste heat energy and puts it tobeneficial use within the vehicle.

The refrigerant cycle of the refrigerant loop 12 is typically the sameas that of a dedicated air conditioning system of a motor vehicleoperating in cooling mode. A two phase refrigerant is circulated throughthe refrigerant loop 12 by the compressor 24, which includes a suctionside 36, also referred to as the low pressure side, and a discharge side38, also referred to as the high pressure side. The suction side of thecompressor receives a low pressure vapor phase refrigerant from theevaporator 22, after absorbing heat from the cold side coolant, andcompresses it to a high pressure vapor phase refrigerant, which is thendischarged to the condenser 18. As the high pressure vapor phaserefrigerant is condensed to a high pressure liquid phase refrigerant inthe condenser 18, heat is transferred to the hot side coolant flowingthrough the hot side chiller 26. Exiting the condenser 18, the highpressure liquid phase refrigerant may pass through a receiver (notshown) to separate any refrigerant vapor, a sub-cooler (not shown) tofurther cool the liquid phase refrigerant, and then to the TXV 20,through which the refrigerant begins to expand into a bubbling liquidphase. The bubbling liquid phase refrigerant enters the evaporator 22and continues to expand into the low pressure vapor refrigerant, whichis then cycled back to the suction side 36 of the compressor 24 torepeat the process.

Referring to FIGS. 2 and 3, the flow paths of the hot and cold coolantloops throughout the vehicle may be reconfigured based on the coolingand heating needs of the vehicle. The hot and cold coolant loops mayinclude a myriad of interconnecting branches with remotely activatedvalves 40 at strategic nodes that may be reconfigured to redefine theflow paths of the hot and cold loops to selectively provide hot or coldcoolant flow to designated heat exchangers. For example, shown in FIG. 2is the Unitary HPAC System 10 operating in cooling mode. The coldcoolant loop (shown in single dashed lines) is configured to flow to acomfort heat exchanger 42 to cool the air to the occupant compartmentand to a battery heat exchanger 46 to cool the batteries, while the hotcoolant loop (shown in double dashed lines) is configured to dissipatethe heat through an external heat exchanger 44. Shown in FIG. 3, in heatpump mode, the hot coolant loop (shown in double dashed lines) may beredirected to the comfort heat exchanger 42 to heat the air to theoccupant compartment and to battery heat exchanger 46 to maintain thebatteries at an optimal operating temperature, while the cold coolantloop (shown in single dashed lines) is directed to an ancillary heatexchangers 48 to scavenge waste heat from the vehicle's electronics orfrom the external ambient air. Unlike the known methods of operating anair-conditioning system in heat pump mode, the refrigerant loop 12 ofthe current invention is never reversed; therefore there is no need toreinforce the refrigerant tubing and fittings throughout the systemsince the low pressure side 38 of the refrigerant loop 12 is not subjectto the high pressure refrigerant.

Shown in FIG. 4 is a compact Unitary HPAC 100 in accordance with anembodiment of the invention for the Unitary HPAC System 10 disclosedabove. The Unitary HPAC 100 shown includes an integral condenser/hotside chiller assembly 102, a receiver 104, a sub-cooler 106, a thermalexpansion valve (TXV) 108, and an integral evaporator/cold side chillerassembly 110. The Unitary HPAC 100 also includes an electrically drivencompressor 112 for the circulation of a typical two-phase refrigerantthrough a series of refrigerant tubes 113 and electrically driven hotside and cold side coolant pumps 114, 116 configured to hydraulicallyconnect to the hot coolant loop and cold coolant loop, respectively. Theliquid coolant used in the hot and coolant loops is generally a mixtureof 70% glycol-30% water, which prevents the coolant from freezing orbecoming too viscous at the low temperatures needed in integralevaporator/cold side chiller assembly 110.

The integral condenser/hot side chiller assembly 110 is a plate-typeheat exchanger assembly having a plurality of stamped metal plates 120stacked and brazed between an upstream end plate 126 and a downstreamend plate 128. The stamped metal plates include features known to thoseof ordinary skill in the art, such as openings, bosses about selectedopenings, and flanges, which when stacked, define a refrigerantpassageway for high pressure refrigerant flow and a separate hot coolantpassageway for hot coolant flow. The plates may include numerous contactpoints established between adjacent plates to induce turbulence to thefluids flowing therethrough to provide a high heat transferco-efficient.

The flows of the hot refrigerant and hot coolant through the integralcondenser/hot side chiller assembly 102 are non-contact; in other words,the two fluids are not intermingle, but are in thermal communicationwith each other, and may be concurrent or countercurrent flow. Heatenergy from the higher temperature refrigerant is transferred to thelower temperature hot coolant, thereby increasing the temperature of thehot coolant as it leaves the integral condenser/hot side chillerassembly 102 and returning to the hot coolant loop (not-shown). Theupstream end plate 126 includes a refrigerant inlet 130 in fluidcommunication with the discharge side 118 of the electrically drivencompressor 112 and a hot coolant inlet 134 in fluid communication withthe hot side coolant pump 116. The downstream end plate 128 includes arefrigerant outlet 132 in fluid communication with the receiver 104 anda hot coolant outlet 136 configured to hydraulically connect to the hotcoolant loop. Similarly, the downstream sub-cooler assembly 106 andintegral evaporator/cold side chiller assembly 110 may also beplate-type heat exchangers. The integral evaporator/cold side chillerassembly 110 includes a cold coolant inlet 138 and outlet 140, in whichthe cold coolant outlet 140 is adapted to hydraulically connect to thecold coolant loop (not shown).

Unlike a traditional air conditioning system, where the refrigerant sidecomponents are remotely dispersed throughout the engine bay and withinthe HVAC module, the refrigeration components of the Unitary HPAC 100including the integral condenser/hot side chiller assembly 102, receiver104, sub-cooler assembly 106, TXV 108, integral evaporator/cold sidechiller assembly 110, and electrically driving compressor 112 andcoolant pumps 114, 116 may be all mounted onto a single platform 142measuring 376 mm by 220 mm or less. The components may even be encloseda housing, having a similar sized base and a height of less than 212 mm,which is approximately the size of a typical bread box, for ease ofhandling and protection against the environment. The centralizedlocation of the components that form the Unitary HPAC 100 allows the useof shorter length refrigerant tubes 113 which are manufactured from arefrigerant impermeable material, such as stainless steel, aluminum,and/or copper. The shortened length refrigerant impermeable tubes 113minimize refrigerant leaks and moisture infiltration; thereby allowingthe use of a smaller receiver 104, since a large volume of refrigerantreserve is not required. The reduction of moisture infiltration reducesor eliminates the volume of desiccant needed, thereby resulting in amore compact Unitary HPAC 100. Due to its compact size, the Unitary HPAC100 may be installed in virtually any location within a motor vehiclethat can fit a bread box, such as within the trunk, under the hood,within the dashboard, or even under the seats.

Shown in FIGS. 5 through 7 is an alternative embodiment of the UnitaryHPAC 200, in which the integral condenser/hot side chiller assembly 102,the receiver 104, the sub-cooler 106, the thermal expansion valve (TXV)108, and the integral evaporator/cold side chiller assembly of theUnitary HPAC 100 shown in FIG. 4 is replaced by a single compactplate-type HPAC heat exchanger 201 assembled from a plurality of stackedand brazed metallic plates. An accumulator 294 may be provideddownstream, with respect to the flow of refrigerant, of the plate-typeHPAC heat exchanger 201 and upstream of the compressor 212. Theplate-type HPAC heat exchanger 201 includes essentially three joinedheat exchanger portions working in conjunction as one integral unit, inwhich a refrigerant is used to transfer heat energy from a cold coolantloop to a hot coolant loop, thereby cooling the cold coolant loop andheating the hot coolant loop.

Best shown in FIGS. 6 and 7, the plate-type HPAC heat exchanger 201includes a condenser/hot side chiller portion 202 and an evaporator/coldside chiller 206 portion, with an internal heat exchanger (IHX) portion204 sandwiched therebetween. The IHX portion 204, together with anintegrated refrigerant expansion device 256 located within theevaporator/cold side chiller portion 206 provides an even more compactUnitary HPAC. The plate-type HPAC heat exchanger 201 together with theassociated electrically driven compressor 212 and coolant pumps 214, 216may be mounted onto a platform 242 or enclosing in a housing measuring376 mm by 220 mm by 175 mm or smaller.

Referring to FIGS. 6 and 7, the condenser/hot side chiller portion 202is essentially a plate-type heat exchanger formed of a plurality ofstamped metal plates stacked between an upstream end plate 270 and firstboundary plate 208. The upstream end plate 270 includes a high pressurerefrigerant inlet 258 in fluid communication with the high pressuredischarge side 218 of the electrically driven compressor 212. The firstboundary plate 208 includes a high pressure vapor refrigerant IHX port260 for refrigerant discharge to the IHX portion 204. However, unlikethe first embodiment, the upstream end plate 270 includes both a hotcoolant inlet 234 and a hot coolant outlet 236. The stamped metal platesinclude portions in which are formed first and second flow spaces, whichwhen stacked and brazed defines a high pressure refrigerant passageway262 for refrigerant flow from high pressure inlet 258 to the highpressure refrigerant IHX port 260, and a separate hot coolant passageway264 for hot coolant flow from the hot coolant inlet 234 to the hotcoolant outlet 236. The high pressure refrigerant passageway 262 and thehot coolant passageway 264 are non-contact, but in thermalcommunication, in which heat energy from the higher temperature highpressure refrigerant is transferred to the lower temperature hotcoolant. The hot coolant inlet 234 and hot coolant outlet 236 areconfigured to hydraulically connect to a hot coolant loop.

The IHX portion 204 is also a plate-type heat exchanger assembled from aplurality of stamped metal plates stacked between the first and a secondboundary plates 208, 210, which joins the IHX portion 204 to thecondenser/hot side chiller and evaporator/cold side chiller portions202, 206, respectively. The stacked metal plates include portions, inwhich are formed first and second flow spaces, which when stacked andbrazed defines an IHX high pressure refrigerant channel 266 and an IHXlow pressure refrigerant channel 268. The second boundary plate 210defines a low pressure refrigerant port 291, in hydraulic communicationwith the IHX low pressure refrigerant channel 268. The flow of andeffects of the non-contact high and low pressure refrigerants flowingthrough the IHX high pressure refrigerant channel 266 and IHX lowpressure refrigerant channel 268 will be discussed in detail below.

The evaporator/cold side chiller portion 206 is also essentially aplate-type heat exchanger formed of a plurality of stamped metal platesstacked and assembled between the second boundary 210 and a downstreamend plate 272. The downstream end plate 272 includes a cold coolantinlet 274, a cold coolant outlet 276, and a low pressure refrigerantoutlet 278. The stacked metal plates include portions having a pluralityof openings and bosses surrounding selected openings to define a coldcoolant passageway 288 that is in hydraulic communication between thecool coolant inlet 276 and outlet 278, a refrigerant expansion chamber280 extending in a direction toward the downstream end plate 272, and alow pressure refrigerant passageway 290 hydraulically connecting therefrigerant expansion chamber 280 adjacent to the downstream end plate272 back toward the IHX low pressure port 291. A tubular expansiondevice 256 having an inlet end 284 and an outlet end 286 is disposed inthe refrigerant expansion chamber 280. The tubular expansion deviceinlet 284 is in fluid communication with the IHX high pressurerefrigerant channel 266 and the expansion device outlet 286 terminateswithin the refrigerant expansion chamber 280 in the direction of thedownstream end plate 272.

Shown in FIG. 6 is schematic of a cross-section of the plate-type HPACHeat Exchanger 201 showing the paths of the hot coolant passageway 264through the condenser/hot side chiller portion 202 and cold coolantpassageway 288 through the evaporator/cold side chiller portion 206.Also shown in FIG. 6 is the flow path of refrigerant as it travelsthrough each of the condenser/hot side chiller portion 202, IHX portion204, and evaporator/cold side chiller 206 portion. For clarity ofillustration, the path of the coolant passageways are simplified as aU-path, but in actuality, the paths of the coolants may be concurrent orcounter-current of that of the refrigerant passageways defined withineach respective portion. What is important is that the flow of coolantand refrigerant do not co-mingle and that there is thermal communicationfor heat transfer between the respective fluids flowing within each ofthe three portions 202, 204, 206.

Referring to condenser/hot side chiller portion 202 shown in FIG. 6, thehigh pressure refrigerant enters the high pressure refrigerant inlet 258of the condenser/hot side chiller portion 202 and travels through thehigh pressure refrigerant passageway 264 to the IHX high pressure port260 of the IHX portion 204. The lower temperature hot coolant enters thehot coolant inlet 234, travels through the hot coolant passageway 264,and exits through the hot coolant outlet 236. As the high pressurerefrigerant and hot coolant travels through their respectivepassageways, heat energy is transferred from the higher temperature highpressure refrigerant to the lower temperature hot coolant, therebycondensing the high pressure vapor refrigerant to a high pressure liquidrefrigerant.

Referring to IHX portion 204 shown in FIG. 6, the high pressure liquidrefrigerant enters the IHX high pressure port 260, travels through theIHX high pressure refrigerant channel 266 to the expansion device inlet284. Low pressure refrigerant enters a IHX low pressure port 260provided on the second boundary plate 210, flows through the IHX lowpressure channel 268, and exits the plate-type HPAC heat exchanger viathe low pressure refrigerant exit header 292, which extends through theevaporator/cold side chiller portion 206 and in hydraulic communicationwith the low pressure refrigerant outlet 278. The high pressurerefrigerant flowing through the IHX high pressure channel 266 and thelow pressure refrigerant flowing through the IHX low pressure channel268 are non-contact, in other words, are not intermingled, but are inthermal communication. A portion of the remaining heat energy from thehigh pressure refrigerant after leaving the condenser/hot side chillerportion 202 is transferred to the lower temperature low pressurerefrigerant from the evaporator/cold side chiller portion 206. The IHXportion 204 increases the amount of sub-cooling of the high pressureliquid refrigerant prior to the expansion device 256 which increases theperformance of evaporator/cold side chiller assembly 206. The heatenergy transferred to the low pressure vapor refrigerant exiting theevaporator/cold side chiller portion 206 increases the amount ofsuperheat to the compressor 212, thereby reducing the likelihood ofliquid entering the compressor 212. Additionally, the high side pressureis lower resulting in lower stress on high side refrigerant components,thereby allowing the use of lower gage refrigerant tubing and fittingson both the low and high pressure side. Furthermore, the IHX portion 204provides additional capacity for the storage of excess refrigerant,thereby eliminating the need for an external receiver, which furtherreduces the footprint of the Unitary HPAC.

Referring to the evaporator/cold side chiller portion 206 shown in FIG.6, the high pressure liquid refrigerant exiting the IHX portion 204enters the inlet 284 of the expansion device 256 which conveys therefrigerant into the expansion chamber 280 of the evaporator/cold sidechiller portion 206. The high pressure liquid refrigerant begins toexpand into a bubbling liquid as it exits the expansion device outlet286 into the expansion chamber 280 toward the downstream plate. Therefrigerant then flows through the low pressure refrigerant passageway290 back toward the second boundary plate 210 and continues to expandinto a vapor phase as it absorb the heat energy form the cold coolantflowing through the cold coolant passageway 288. The low pressure vaporrefrigerant then enters the IHX low pressure inlet 291 as describedabove before exiting the evaporator/cold side chiller portion 206 by wayof the refrigerant exit header 292. In other words, the spent lowertemperature low pressure vapor refrigerant from the evaporator/cold sidechiller portion 206 is used to pre-cool the relatively highertemperature high pressure liquid refrigerant exiting the condenser/hotside chiller portion 202 in the IHX portion 204 prior to the internalexpansion device 256.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the intentions without departing fromthe essential scope thereof. Therefore, it is intended that theinvention not be limited to the particular embodiment disclosed as thebest mode contemplated for carrying out this invention, but that theinvention will include all embodiments falling within the scope of theappended claims.

Having described the invention, it is claimed:
 1. A unitary heat pumpair conditioner (Unitary HPAC), comprising: a plate-type HPAC heatexchanger having a plurality of plates stacked and hermetically sealedbetween an upstream end plate and a downstream end plate, defining: afirst heat exchanger portion configured to receive a refrigerant flowand a hot side coolant flow having a lower temperature than therefrigerant flow, wherein said refrigerant flow is in non-contactthermal communication with the hot side coolant flow, whereby heatenergy is transferred from the refrigerant flow to the hot side coolantflow; and a second heat exchanger portion is configured to receive arefrigerant flow exiting from said first heat exchanger portion and acold side coolant flow having a higher temperature than the refrigerantflow exiting from said first heat exchanger portion, wherein the coldside coolant flow is in non-contact thermal communication with therefrigerant flow, whereby heat energy is transferred from the cold sidecoolant flow to the refrigerant flow; wherein said first and second heatexchanger portions define a single unitary structure having a continuoustorturous refrigerant passageway in thermal contact with both the coldside coolant flow and the hot side coolant flow.
 2. The Unitary HPAC ofclaim 1, wherein said plate-type HPAC heat exchanger further includes:an internal heat exchanger portion configured to receive the refrigerantflow exiting from said first heat exchanger portion before beingreceived by said second heat exchanger portion and a refrigerant flowfrom said second heat exchanger portion before exiting said second heatexchanger portion, wherein the temperature of the refrigerant flowexiting said first heat exchanger portion is higher than temperature ofthe refrigerant flow exiting from said second heat exchanger portion,and wherein the refrigerant flow from said first heat exchanger portionis in non-contact thermal communication with the refrigerant flow fromthe second heat exchanger portion, whereby heat energy is transferredfrom the refrigerant flow exiting from said first heat exchanger portionto the lower temperature refrigerant flow from said second heatexchanger portion.
 3. The Unitary HPAC of claim 2, wherein said internalheat exchanger portion is sandwiched between said first heat exchangerportion and said second heat exchanger portion, thereby forming a singleunit integral plate-type HPAC heat exchanger.
 4. The Unitary HPAC ofclaim 1, wherein said first heat exchanger portion comprises: a hot sidecoolant inlet, a hot side coolant outlet, and a high pressurerefrigerant inlet disposed on said upstream end plate, a hot sidecoolant passageway in fluid communication with said hot side coolantinlet and hot side coolant outlet; a first boundary plate spaced fromsaid upstream end plate defining a high pressure refrigerant port; and ahigh pressure refrigerant passageway in fluid communication with saidrefrigerant inlet of said upstream plate and said high pressurerefrigerant port of first boundary plate; wherein said hot side coolantpassageway and said high pressure refrigerant passageway are innon-contact thermal communication.
 5. The Unitary HPAC of claim 4,wherein said second heat exchanger portion comprises: a cold sidecoolant inlet, a cold side coolant outlet, and a low pressurerefrigerant outlet disposed on said downstream end plate, a cold sidecoolant passageway in fluid communication with said cold side coolantinlet and cold side coolant outlet; an elongated refrigerant expansionchamber extending in a direction toward said downstream end plate; and alow pressure refrigerant passageway in fluid communication with saidrefrigerant expansion chamber and said low pressure refrigerant outlet;wherein said cold side coolant passageway and said low pressurerefrigerant passageway are in non-contact thermal communication.
 6. Aplate-type HPAC heat exchanger comprising: a first heat exchangerportion having an upstream end plate including a high pressurerefrigerant inlet; a second heat exchanger portion having a downstreamend plate including a low pressure refrigerant outlet; an internal heatexchanger having a first boundary plate and a second boundary plate,wherein said internal heat exchanger is integrally sandwiched betweensaid first heat exchanger portion and said second heat exchangerportion; a refrigerant passageway extending from said high pressurerefrigerant inlet to said low pressure refrigerant outlet, defining ahigh pressure refrigerant flow passageway through said first heatexchanger portion and a low pressure refrigerant flow passageway throughsaid second heat exchanger portion; a hot side coolant passageway innon-contact thermal communication with said high pressure refrigerantpassageway; and a cold side coolant passageway in non-contact thermalcommunication with said low pressure refrigerant passageway.
 7. Theplate-type HPAC heat exchanger of claim 6, wherein said internal heatexchanger includes a high pressure refrigerant channel in hydrauliccommunication with said high pressure refrigerant passageway of firstheat exchanger portion, and a low pressure refrigerant channel inhydraulic communication with said low pressure refrigerant outlet ofsecond heat exchanger portion.